Systems and methods of for providing multi-mode transport layer compression

ABSTRACT

Systems and methods are disclosed for communicating compressed and uncompressed content over a transport layer connection established by an appliance between a client and a server. One method comprises the steps of: establishing, by an appliance, a transport layer connection between a client and a server, and receiving, by the appliance, a first response from the server to a first client request, and a second response from the server to a second client request The first response and the second response has uncompressed data. The method includes transmitting, by the appliance, the first response to the client. The appliance identifies first type of compression from a plurality of compression types for compressing the second response to the client, compresses the second response based on the identified compression type, and transmits the compressed second response to the client.

FIELD OF THE INVENTION

The present invention generally relates to data communication networks.In particular, the present invention relates to systems and methods fortransmitting compressed and uncompressed content to a client via thesame transport layer connection.

BACKGROUND OF THE INVENTION

During network communications between a client and a server, somecompression aware browsers are provided with compressed data, such ascompressed HyperText Markup Language (HTML) data. However some browsershave problems handling some content in compressed form. For example, theMicrosoft Internet Explorer browser is designed to handle compressedrich text formatted content or compressed Microsoft PowerPoint contentwhile other browsers are not. In one case, some versions of the browserplugin Macromedia FlashPlayer not handle compressed plain text. Inanother case, some versions of the Netscape browser do not handlecompressed java script. In another example, some browsers do not handlecompressed KHTML, which is the HTML produced from the open source KHTMLengine. In yet another example, some browsers do not handle compressedcascading style sheets (CSS), such as Netscape version 4.0.

One way to solve compression issues with a browser is to not compresscontent for certain types of browsers. However, this has the undesirableeffect of not obtaining the benefits of compression, such as toaccelerate communications between a client and a server or to improvethe response time to a user. By foregoing compressing of contenttransmitted to the browser, the opportunity to accelerate communicationsby compressing large content is missed. The uncompressed large contentmay slow down network communications or impact the user's experience inviewing or interacting with the content.

It would, therefore, be desirable to provide systems and methods totransmit both compressed and uncompressed content to a client.

BRIEF SUMMARY OF THE INVENTION

The present invention provides a solution to transmitting compressed anduncompressed content to an application in a manner independent to thecompression capabilities of the appliance. The appliance describedherein provides for the transmission of compressed and uncompressedcontent over the same transport layer connection between a client and aserver. The appliance transmits compressed content to a client agent,which decompresses the content and provides the uncompressed content toan application on the client. The appliance can accelerate or otherwiseimprove the speed of delivery of content or the transmission of networkcommunications between a client and server in a manner not dependent onthe compression capabilities or compression awareness of the applicationon the client and/or the application on the server. Additionally, theappliance can apply one of a plurality of compression techniques tonetwork communications based on a compression policy and/or informationassociated with the communication, such as IP layer information,protocol, or content or type of object of the communications.

In one aspect, the present invention is related to a method forcommunicating compressed and uncompressed content over a transport layerconnection established by an appliance between a client and a server.The method includes establishing, by an appliance, a transport layerconnection between a client and a server. The appliance receives a firstresponse from the server to a first client request, and a secondresponse from the server to a second client request. The first responseand the second response include uncompressed data. The appliancetransmits the first response to the client. The method includesidentifying, by the appliance, a first type of compression from aplurality of compression types for compressing the second response tothe client compressing the second response based on the identifiedcompression type, and transmitting, the compressed second response tothe client.

In one embodiment, the method includes determining, by the appliance, atype of object included in one of the first response or the secondresponse. In another embodiment, the method includes identifying, by theappliance, the type of compression for compressing the second responsebased on the type of object. In some embodiments, the method includesconfiguring, via the appliance, a rule identifying the type ofcompression associated with the type of object. In other embodiments,the appliance identifies the type of compression for compressing thesecond response based on a protocol of the second response. In anotherembodiment, the appliance identifies the type of compression forcompressing the second response based on a compression policy. In someembodiments, the type of compression includes one of the following: agzip compression, a deflate compression, and a delta compression.

In other embodiments, the method includes identifying, by the appliance,for a third response to the client a second type of compression from theplurality of compression types, compressing the third response based onthe second type of compression, and transmitting the compressed thirdresponse to the client. In another embodiments, the method includesidentifying, by the appliance, for a third response to a second client asecond type of compression from the plurality of compression types,compressing the third response based on the second type of compression,and transmitting the compressed third response to the second client.

In one embodiment, the method establishes, by the appliance, a SecureSocket Layer (SSL) session via the transport layer connection betweenthe client and the server. In another embodiment, the method includesaccelerating, by the appliance, transmission of one of the firstresponse or the compressed second response using one or more of thefollowing techniques: Transport Control Protocol (TCP) connectionpooling, TCP connection multiplexing, TCP buffering, and caching.

The details of various embodiments of the invention are set forth in theaccompanying drawings and the description below.

BRIEF DESCRIPTION OF THE FIGURES

The foregoing and other objects, aspects, features, and advantages ofthe invention will become more apparent and better understood byreferring to the following description taken in conjunction with theaccompanying drawings, in which:

FIG. 1A is a block diagram of an embodiment of a network environment fora client to access a server via an appliance;

FIG. 1B is a block diagram of an embodiment of an environment fordelivering a computing environment from a server to a client via anappliance;

FIGS. 1C and 1D are block diagrams of embodiments of a computing device;

FIG. 2A is a block diagram of an embodiment of an appliance forprocessing communications between a client and a server;

FIG. 2B is a block diagram of another embodiment of an appliance foroptimizing, accelerating, load-balancing and routing communicationsbetween a client and a server;

FIG. 3 is a block diagram of an embodiment of a client for communicatingwith a server via the appliance;

FIG. 4 is a block diagram of an embodiment of an appliance for providingmulti-mode compression as described herein; and

FIG. 5 is a flow diagram depicting steps of an embodiment of a methodfor practicing multi-mode compression.

The features and advantages of the present invention will become moreapparent from the detailed description set forth below when taken inconjunction with the drawings, in which like reference charactersidentify corresponding elements throughout. In the drawings, likereference numbers generally indicate identical, functionally similar,and/or structurally similar elements.

DETAILED DESCRIPTION OF THE INVENTION

A. Network and Computing Environment

Prior to discussing the specifics of embodiments of the systems andmethods of an appliance and/or client, it may be helpful to discuss thenetwork and computing environments in which such embodiments may bedeployed. Referring now to FIG. 1A, an embodiment of a networkenvironment is depicted. In brief overview, the network environmentcomprises one or more clients 102 a-102 n (also generally referred to aslocal machine(s) 102, or client(s) 102) in communication with one ormore servers 106 a-106 n (also generally referred to as server(s) 106,or remote machine(s) 106) via one or more networks 104, 104′ (generallyreferred to as network 104). In some embodiments, a client 102communicates with a server 106 via an appliance 200.

Although FIG. 1A shows a network 104 and a network 104′ between theclients 102 and the servers 106, the clients 102 and the servers 106 maybe on the same network 104. The networks 104 and 104′ can be the sametype of network or different types of networks. The network 104 and/orthe network 104′ can be a local-area network (LAN), such as a companyIntranet, a metropolitan area network (MAN), or a wide area network(WAN), such as the Internet or the World Wide Web. In one embodiment,network 104′ may be a private network and network 104 may be a publicnetwork. In some embodiments, network 104 may be a private network andnetwork 104′ a public network. In another embodiment, networks 104 and104′ may both be private networks. In some embodiments, clients 102 maybe located at a branch office of a corporate enterprise communicatingvia a WAN connection over the network 104 to the servers 106 located ata corporate data center.

The network 104 and/or 104′ be any type and/or form of network and mayinclude any of the following: a point to point network, a broadcastnetwork, a wide area network, a local area network, a telecommunicationsnetwork, a data communication network, a computer network, an ATM(Asynchronous Transfer Mode) network, a SONET (Synchronous OpticalNetwork) network, a SDH (Synchronous Digital Hierarchy) network, awireless network and a wireline network. In some embodiments, thenetwork 104 may comprise a wireless link, such as an infrared channel orsatellite band. The topology of the network 104 and/or 104′ may be abus, star, or ring network topology. The network 104 and/or 104′ andnetwork topology may be of any such network or network topology as knownto those ordinarily skilled in the art capable of supporting theoperations described herein.

As shown in FIG. 1A, the appliance 200, which also may be referred to asan interface unit 200 or gateway 200, is shown between the networks 104and 104′. In some embodiments, the appliance 200 may be located onnetwork 104. For example, a branch office of a corporate enterprise maydeploy an appliance 200 at the branch office. In other embodiments, theappliance 200 may be located on network 104′. For example, an appliance200 may be located at a corporate data center. In yet anotherembodiment, a plurality of appliances 200 may be deployed on network104. In some embodiments, a plurality of appliances 200 may be deployedon network 104′. In one embodiment, a first appliance 200 communicateswith a second appliance 200′. In other embodiments, the appliance 200could be a part of any client 102 or server 106 on the same or differentnetwork 104,104′ as the client 102. One or more appliances 200 may belocated at any point in the network or network communications pathbetween a client 102 and a server 106.

In one embodiment, the system may include multiple, logically-groupedservers 106. In these embodiments, the logical group of servers may bereferred to as a server farm 38. In some of these embodiments, theserves 106 may be geographically dispersed. In some cases, a farm 38 maybe administered as a single entity. In other embodiments, the serverfarm 38 comprises a plurality of server farms 38. In one embodiment, theserver farm executes one or more applications on behalf of one or moreclients 102.

The servers 106 within each farm 38 can be heterogeneous. One or more ofthe servers 106 can operate according to one type of operating systemplatform (e.g., WINDOWS NT, manufactured by Microsoft Corp. of Redmond,Wash.), while one or more of the other servers 106 can operate onaccording to another type of operating system platform (e.g., Unix orLinux). The servers 106 of each farm 38 do not need to be physicallyproximate to another server 106 in the same farm 38. Thus, the group ofservers 106 logically grouped as a farm 38 may be interconnected using awide-area network (WAN) connection or medium-area network (MAN)connection. For example, a farm 38 may include servers 106 physicallylocated in different continents or different regions of a continent,country, state, city, campus, or room. Data transmission speeds betweenservers 106 in the farm 38 can be increased if the servers 106 areconnected using a local-area network (LAN) connection or some form ofdirect connection.

Servers 106 may be referred to as a file server, application server, webserver, proxy server, or gateway server. In some embodiments, a server106 may have the capacity to function as either an application server oras a master application server. In one embodiment, a server 106 mayinclude an Active Directory. The clients 102 may also be referred to asclient nodes or endpoints. In some embodiments, a client 102 has thecapacity to function as both a client node seeking access toapplications on a server and as an application server providing accessto hosted applications for other clients 102 a-102 n.

In some embodiments, a client 102 communicates with a server 106. In oneembodiment, the client 102 communicates directly with one of the servers106 in a farm 38. In another embodiment, the client 102 executes aprogram neighborhood application to communicate with a server 106 in afarm 38. In still another embodiment, the server 106 provides thefunctionality of a master node. In some embodiments, the client 102communicates with the server 106 in the farm 38 through a network 104.Over the network 104, the client 102 can, for example, request executionof various applications hosted by the servers 106 a-106 n in the farm 38and receive output of the results of the application execution fordisplay. In some embodiments, only the master node provides thefunctionality required to identify and provide address informationassociated with a server 106′ hosting a requested application.

In one embodiment, the server 106 provides functionality of a webserver. In another embodiment, the server 106 a receives requests fromthe client 102, forwards the requests to a second server 106 b andresponds to the request by the client 102 with a response to the requestfrom the server 106 b. In still another embodiment, the server 106acquires an enumeration of applications available to the client 102 andaddress information associated with a server 106 hosting an applicationidentified by the enumeration of applications. In yet anotherembodiment, the server 106 presents the response to the request to theclient 102 using a web interface. In one embodiment, the client 102communicates directly with the server 106 to access the identifiedapplication. In another embodiment, the client 102 receives applicationoutput data, such as display data, generated by an execution of theidentified application on the server 106.

Referring now to FIG. 1B, a network environment for delivering and/oroperating a computing environment on a client 102 is depicted. In someembodiments, a server 106 includes an application delivery system 190for delivering a computing environment or an application and/or datafile to one or more clients 102. In brief overview, a client 10 is incommunication with a server 106 via network 104, 104′ and appliance 200.For example, the client 102 may reside in a remote office of a company,e.g., a branch office, and the server 106 may reside at a corporate datacenter. The client 102 comprises a client agent 120, and a computingenvironment 15. The computing environment 15 may execute or operate anapplication that accesses, processes or uses a data file. The computingenvironment 15, application and/or data file may be delivered via theappliance 200 and/or the server 106.

In some embodiments, the appliance 200 accelerates delivery of acomputing environment 15, or any portion thereof, to a client 102. Inone embodiment, the appliance 200 accelerates the delivery of thecomputing environment 15 by the application delivery system 190. Forexample, the embodiments described herein may be used to acceleratedelivery of a streaming application and data file processable by theapplication from a central corporate data center to a remote userlocation, such as a branch office of the company. In another embodiment,the appliance 200 accelerates transport layer traffic between a client102 and a server 106. The appliance 200 may provide accelerationtechniques for accelerating any transport layer payload from a server106 to a client 102, such as: 1) transport layer connection pooling, 2)transport layer connection multiplexing, 3) transport control protocolbuffering, 4) compression and 5) caching. In some embodiments, theappliance 200 provides load balancing of servers 106 in responding torequests from clients 102. In other embodiments, the appliance 200 actsas a proxy or access server to provide access to the one or more servers106. In another embodiment, the appliance 200 provides a secure virtualprivate network connection from a first network 104 of the client 102 tothe second network 104′ of the server 106, such as an SSL VPNconnection. It yet other embodiments, the appliance 200 providesapplication firewall security, control and management of the connectionand communications between a client 102 and a server 106.

In some embodiments, the application delivery management system 190provides application delivery techniques to deliver a computingenvironment to a desktop of a user, remote or otherwise, based on aplurality of execution methods and based on any authentication andauthorization policies applied via a policy engine 195. With thesetechniques, a remote user may obtain a computing environment and accessto server stored applications and data files from any network connecteddevice 100. In one embodiment, the application delivery system 190 mayreside or execute on a server 106. In another embodiment, theapplication delivery system 190 may reside or execute on a plurality ofservers 106 a-106 n. In some embodiments, the application deliverysystem 190 may execute in a server farm 38. In one embodiment, theserver 106 executing the application delivery system 190 may also storeor provide the application and data file. In another embodiment, a firstset of one or more servers 106 may execute the application deliverysystem 190, and a different server 106 n may store or provide theapplication and data file. In some embodiments, each of the applicationdelivery system 190, the application, and data file may reside or belocated on different servers. In yet another embodiment, any portion ofthe application delivery system 190 may reside, execute or be stored onor distributed to the appliance 200, or a plurality of appliances.

The client 102 may include a computing environment 15 for executing anapplication that uses or processes a data file. The client 102 vianetworks 104, 104′ and appliance 200 may request an application and datafile from the server 106. In one embodiment, the appliance 200 mayforward a request from the client 102 to the server 106. For example,the client 102 may not have the application and data file stored oraccessible locally. In response to the request, the application deliverysystem 190 and/or server 106 may deliver the application and data fileto the client 102. For example, in one embodiment, the server 106 maytransmit the application as an application stream to operate incomputing environment 15 on client 102.

In some embodiments, the application delivery system 190 comprises anyportion of the Citrix Access Suite™ by Citrix Systems, Inc., such as theMetaFrame or Citrix Presentation Server™ and/or any of the Microsoft®Windows Terminal Services manufactured by the Microsoft Corporation. Inone embodiment, the application delivery system 190 may deliver one ormore applications to clients 102 or users via a remote-display protocolor otherwise via remote-based or server-based computing. In anotherembodiment, the application delivery system 190 may deliver one or moreapplications to clients or users via steaming of the application.

In one embodiment, the application delivery system 190 includes a policyengine 195 for controlling and managing the access to, selection ofapplication execution methods and the delivery of applications. In someembodiments, the policy engine 195 determines the one or moreapplications a user or client 102 may access. In another embodiment, thepolicy engine 195 determines how the application should be delivered tothe user or client 102, e.g., the method of execution. In someembodiments, the application delivery system 190 provides a plurality ofdelivery techniques from which to select a method of applicationexecution, such as a server-based computing, streaming or delivering theapplication locally to the client 120 for local execution.

In one embodiment, a client 102 requests execution of an applicationprogram and the application delivery system 190 comprising a server 106selects a method of executing the application program. In someembodiments, the server 106 receives credentials from the client 102. Inanother embodiment, the server 106 receives a request for an enumerationof available applications from the client 102. In one embodiment, inresponse to the request or receipt of credentials, the applicationdelivery system 190 enumerates a plurality of application programsavailable to the client 102. The application delivery system 190receives a request to execute an enumerated application. The applicationdelivery system 190 selects one of a predetermined number of methods forexecuting the enumerated application, for example, responsive to apolicy of a policy engine. The application delivery system 190 mayselect a method of execution of the application enabling the client 102to receive application-output data generated by execution of theapplication program on a server 106. The application delivery system 190may select a method of execution of the application enabling the localmachine 10 to execute the application program locally after retrieving aplurality of application files comprising the application. In yetanother embodiment, the application delivery system 190 may select amethod of execution of the application to stream the application via thenetwork 104 to the client 102.

A client 102 may execute, operate or otherwise provide an application,which can be any type and/or form of software, program, or executableinstructions such as any type and/or form of web browser, web-basedclient, client-server application, a thin-client computing client, anActiveX control, or a Java applet, or any other type and/or form ofexecutable instructions capable of executing on client 102. In someembodiments, the application may be a server-based or a remote-basedapplication executed on behalf of the client 102 on a server 106. In oneembodiments the server 106 may display output to the client 102 usingany thin-client or remote-display protocol, such as the IndependentComputing Architecture (ICA) protocol manufactured by Citrix Systems,Inc. of Ft. Lauderdale, Fla. or the Remote Desktop Protocol (RDP)manufactured by the Microsoft Corporation of Redmond, Wash. Theapplication can use any type of protocol and it can be, for example, anHTTP client, an FTP client, an Oscar client, or a Telnet client. Inother embodiments, the application comprises any type of softwarerelated to VoIP communications, such as a soft IP telephone. In furtherembodiments, the application comprises any application related toreal-time data communications, such as applications for streaming videoand/or audio.

In some embodiments, the server 106 or a server farm 38 may be runningone or more applications, such as an application providing a thin-clientcomputing or remote display presentation application. In one embodiment,the server 106 or server farm 38 executes as an application, any portionof the Citrix Access Suite™ by Citrix Systems, Inc., such as theMetaFrame or Citrix Presentation Server™, and/or any of the Microsoft®Windows Terminal Services manufactured by the Microsoft Corporation. Inone embodiment, the application is an ICA client, developed by CitrixSystems, Inc. of Fort Lauderdale, Fla. In other embodiments, theapplication includes a Remote Desktop (RDP) client, developed byMicrosoft Corporation of Redmond, Wash. Also, the server 106 may run anapplication, which for example, may be an application server providingemail services such as Microsoft Exchange manufactured by the MicrosoftCorporation of Redmond, Wash., a web or Internet server, or a desktopsharing server, or a collaboration server. In some embodiments, any ofthe applications may comprise any type of hosted service or products,such as GoToMeeting™ provided by Citrix Online Division, Inc. of SantaBarbara, Calif., WebEX™ provided by WebEx, Inc. of Santa Clara, Calif.,or Microsoft Office Live Meeting provided by Microsoft Corporation ofRedmond, Wash.

The client 102, server 106, and appliance 200 may be deployed as and/orexecuted on any type and form of computing device, such as a computer,network device or appliance capable of communicating on any type andform of network and performing the operations described herein. FIGS. 1Cand 1D depict block diagrams of a computing device 100 useful forpracticing an embodiment of the client 102, server 106 or appliance 200.As shown in FIGS. 1C and 1D, each computing device 100 includes acentral processing unit 101, and a main memory unit 122. As shown inFIG. 1C, a computing device 100 may include a visual display device 124,a keyboard 126 and/or a pointing device 127, such as a mouse. Eachcomputing device 100 may also include additional optional elements, suchas one or more input/output devices 130 a-130 b (generally referred tousing reference numeral 130), and a cache memory 140 in communicationwith the central processing unit 101.

The central processing unit 101 is any logic circuitry that responds toand processes instructions fetched from the main memory unit 122. Inmany embodiments, the central processing unit is provided by amicroprocessor unit, such as: those manufactured by Intel Corporation ofMountain View, Calif.; those manufactured by Motorola Corporation ofSchaumburg, Ill.; those manufactured by Transmeta Corporation of SantaClara, Calif.; the RS/6000 processor, those manufactured byInternational Business Machines of White Plains, N.Y.; or thosemanufactured by Advanced Micro Devices of Sunnyvale, Calif. Thecomputing device 100 may be based on any of these processors, or anyother processor capable of operating as described herein.

Main memory unit 122 may be one or more memory chips capable of storingdata and allowing any storage location to be directly accessed by themicroprocessor 101, such as Static random access memory (SRAM), BurstSRAM or SynchBurst SRAM (BSRAM), Dynamic random access memory (DRAM),Fast Page Mode DRAM (FPM DRAM), Enhanced DRAM (EDRAM), Extended DataOutput RAM (EDO RAM), Extended Data Output DRAM (EDO DRAM), BurstExtended Data Output DRAM (BEDO DRAM), Enhanced DRAM (EDRAM),synchronous DRAM (SDRAM), JEDEC SRAM, PC100 SDRAM, Double Data RateSDRAM (DDR SDRAM), Enhanced SDRAM (ESDRAM), SyncLink DRAM (SLDRAM),Direct Rambus DRAM (DRDRAM), or Ferroelectric RAM (FRAM). The mainmemory 122 may be based on any of the above described memory chips, orany other available memory chips capable of operating as describedherein. In the embodiment shown in FIG. 1C, the processor 101communicates with main memory 122 via a system bus 150 (described inmore detail below). FIG. 1C depicts an embodiment of a computing device100 in which the processor communicates directly with main memory 122via a memory port 103. For example, in FIG. 1D the main memory 122 maybe DRDRAM.

FIG. 1D depicts an embodiment in which the main processor 101communicates directly with cache memory 140 via a secondary bus,sometimes referred to as a backside bus. In other embodiments, the mainprocessor 101 communicates with cache memory 140 using the system bus150. Cache memory 140 typically has a faster response time than mainmemory 122 and is typically provided by SRAM, BSRAM, or EDRAM. In theembodiment shown in FIG. 1C, the processor 101 communicates with variousI/O devices 130 via a local system bus 150. Various busses may be usedto connect the central processing unit 101 to any of the I/O devices130, including a VESA VL bus, an ISA bus, an EISA bus, a MicroChannelArchitecture (MCA) bus, a PCI bus, a PCI-X bus, a PCI-Express bus, or aNuBus. For embodiments in which the I/O device is a video display 124,the processor 101 may use an Advanced Graphics Port (AGP) to communicatewith the display 124. FIG. 1D depicts an embodiment of a computer 100 inwhich the main processor 101 communicates directly with I/O device 130via HyperTransport, Rapid I/O, or InfiniBand. FIG. 1D also depicts anembodiment in which local busses and direct communication are mixed: theprocessor 101 communicates with I/O device 130 using a localinterconnect bus while communicating with I/O device 130 directly.

The computing device 100 may support any suitable installation device116, such as a floppy disk drive for receiving floppy disks such as3.5-inch, 5.25-inch disks or ZIP disks, a CD-ROM drive, a CD-R/RW drive,a DVD-ROM drive, tape drives of various formats, USB device, hard-driveor any other device suitable for installing software and programs suchas any client agent 120, or portion thereof. The computing device 100may further comprise a storage device 128, such as one or more hard diskdrives or redundant arrays of independent disks, for storing anoperating system and other related software, and for storing applicationsoftware programs such as any program related to the client agent 120.Optionally, any of the installation devices 116 could also be used asthe storage device 128. Additionally, the operating system and thesoftware can be run from a bootable medium, for example, a bootable CD,such as KNOPPIX®, a bootable CD for GNU/Linux that is available as aGNU/Linux distribution from knoppix.net.

Furthermore, the computing device 100 may include a network interface118 to interface to a Local Area Network (LAN), Wide Area Network (WAN)or the Internet through a variety of connections including, but notlimited to, standard telephone lines, LAN or WAN links (e.g., 802.11,T1, T3, 56 kb, X.25), broadband connections (e.g., ISDN, Frame Relay,ATM), wireless connections, or some combination of any or all of theabove. The network interface 118 may comprise a built-in networkadapter, network interface card, PCMCIA network card, card bus networkadapter, wireless network adapter, USB network adapter, modem or anyother device suitable for interfacing the computing device 100 to anytype of network capable of communication and performing the operationsdescribed herein. A wide variety of I/O devices 130 a-130 n may bepresent in the computing device 100. Input devices include keyboards,mice, trackpads, trackballs, microphones, and drawing tablets. Outputdevices include video displays, speakers, inkjet printers, laserprinters, and dye-sublimation printers. The I/O devices 130 may becontrolled by an I/O controller 123 as shown in FIG. 1C. The I/Ocontroller may control one or more I/O devices such as a keyboard 126and a pointing device 127, e.g., a mouse or optical pen. Furthermore, anI/O device may also provide storage 128 and/or an installation medium116 for the computing device 100. In still other embodiments, thecomputing device 100 may provide USB connections to receive handheld USBstorage devices such as the USB Flash Drive line of devices manufacturedby Twintech Industry, Inc. of Los Alamitos, Calif.

In some embodiments, the computing device 100 may comprise or beconnected to multiple display devices 124 a-124 n, which each may be ofthe same or different type and/or form. As such, any of the I/O devices130 a-130 n and/or the I/O controller 123 may comprise any type and/orform of suitable hardware, software, or combination of hardware andsoftware to support, enable or provide for the connection and use ofmultiple display devices 124 a-124 n by the computing device 100. Forexample, the computing device 100 may include any type and/or form ofvideo adapter, video card, driver, and/or library to interface,communicate, connect or otherwise use the display devices 124 a-124 n.In one embodiment, a video adapter may comprise multiple connectors tointerface to multiple display devices 124 a-124 n. In other embodiments,the computing device 100 may include multiple video adapters, with eachvideo adapter connected to one or more of the display devices 124 a-124n. In some embodiments, any portion of the operating system of thecomputing device 100 may be configured for using multiple displays 124a-124 n. In other embodiments, one or more of the display devices 124a-124 n may be provided by one or more other computing devices, such ascomputing devices 100 a and 100 b connected to the computing device 100,for example, via a network. These embodiments may include any type ofsoftware designed and constructed to use another computer's displaydevice as a second display device 124 a for the computing device 100.One ordinarily skilled in the art will recognize and appreciate thevarious ways and embodiments that a computing device 100 may beconfigured to have multiple display devices 124 a-124 n.

In further embodiments, an I/O device 130 may be a bridge 170 betweenthe system bus 150 and an external communication bus, such as a USB bus,an Apple Desktop Bus, an RS-232 serial connection, a SCSI bus, aFireWire bus, a FireWire 800 bus, an Ethernet bus, an AppleTalk bus, aGigabit Ethernet bus, an Asynchronous Transfer Mode bus, a HIPPI bus, aSuper HIPPI bus, a SerialPlus bus, a SCI/LAMP bus, a FibreChannel bus,or a Serial Attached small computer system interface bus.

A computing device 100 of the sort depicted in FIGS. 1C and 1D typicallyoperate under the control of operating systems, which control schedulingof tasks and access to system resources. The computing device 100 can berunning any operating system such as any of the versions of theMicrosoft® Windows operating systems, the different releases of the Unixand Linux operating systems, any version of the Mac OS® for Macintoshcomputers, any embedded operating system, any real-time operatingsystem, any open source operating system, any proprietary operatingsystem, any operating systems for mobile computing devices, or any otheroperating system capable of running on the computing device andperforming the operations described herein. Typical operating systemsinclude: WINDOWS 3.x, WINDOWS 95, WINDOWS 98, WINDOWS 2000, WINDOWS NT3.51, WINDOWS NT 4.0, WINDOWS CE, and WINDOWS XP, all of which aremanufactured by Microsoft Corporation of Redmond, Wash.; MacOS,manufactured by Apple Computer of Cupertino, Calif.; OS/2, manufacturedby International Business Machines of Armonk, N.Y.; and Linux, afreely-available operating system distributed by Caldera Corp. of SaltLake City, Utah, or any type and/or form of a Unix operating system,among others.

In other embodiments, the computing device 100 may have differentprocessors, operating systems, and input devices consistent with thedevice. For example, in one embodiment the computer 100 is a Treo 180,270, 1060, 600 or 650 smart phone manufactured by Palm, Inc. In thisembodiment, the Treo smart phone is operated under the control of thePalmOS operating system and includes a stylus input device as well as afive-way navigator device. Moreover, the computing device 100 can be anyworkstation, desktop computer, laptop or notebook computer, server,handheld computer, mobile telephone, any other computer, or other formof computing or telecommunications device that is capable ofcommunication and that has sufficient processor power and memorycapacity to perform the operations described herein.

B. Appliance Architecture

FIG. 2A illustrates an example embodiment of the appliance 200. Thearchitecture of the appliance 200 in FIG. 2A is provided by way ofillustration only and is not intended to be limiting. As shown in FIG.2, appliance 200 comprises a hardware layer 206 and a software layerdivided into a user space 202 and a kernel space 204.

Hardware layer 206 provides the hardware elements upon which programsand services within kernel space 204 and user space 202 are executed.Hardware layer 206 also provides the structures and elements which allowprograms and services within kernel space 204 and user space 202 tocommunicate data both internally and externally with respect toappliance 200. As shown in FIG. 2, the hardware layer 206 includes aprocessing unit 262 for executing software programs and services, amemory 264 for storing software and data, network ports 266 fortransmitting and receiving data over a network, and an encryptionprocessor 260 for performing functions related to Secure Sockets Layerprocessing of data transmitted and received over the network. In someembodiments, the central processing unit 262 may perform the functionsof the encryption processor 260 in a single processor. Additionally, thehardware layer 206 may comprise multiple processors for each of theprocessing unit 262 and the encryption processor 260. The processor 262may include any of the processors 101 described above in connection withFIGS. 1C and 1D. In some embodiments, the central processing unit 262may perform the functions of the encryption processor 260 in a singleprocessor. Additionally, the hardware layer 206 may comprise multipleprocessors for each of the processing unit 262 and the encryptionprocessor 260. For example, in one embodiment, the appliance 200comprises a first processor 262 and a second processor 262′. In otherembodiments, the processor 262 or 262′ comprises a multi-core processor.

Although the hardware layer 206 of appliance 200 is generallyillustrated with an encryption processor 260, processor 260 may be aprocessor for performing functions related to any encryption protocol,such as the Secure Socket Layer (SSL) or Transport Layer Security (TLS)protocol. In some embodiments, the processor 260 may be a generalpurpose processor (GPP), and in further embodiments, may be haveexecutable instructions for performing processing of any securityrelated protocol.

Although the hardware layer 206 of appliance 200 is illustrated withcertain elements in FIG. 2, the hardware portions or components ofappliance 200 may comprise any type and form of elements, hardware orsoftware, of a computing device, such as the computing device 100illustrated and discussed herein in conjunction with FIGS. 1C and 1D. Insome embodiments, the appliance 200 may comprise a server, gateway,router, switch, bridge or other type of computing or network device, andhave any hardware and/or software elements associated therewith.

The operating system of appliance 200 allocates, manages, or otherwisesegregates the available system memory into kernel space 204 and userspace 204. In example software architecture 200, the operating systemmay be any type and/or form of Unix operating system although theinvention is not so limited. As such, the appliance 200 can be runningany operating system such as any of the versions of the Microsoft®Windows operating systems, the different releases of the Unix and Linuxoperating systems, any version of the Mac OS® for Macintosh computers,any embedded operating system, any network operating system, anyreal-time operating system, any open source operating system, anyproprietary operating system, any operating systems for mobile computingdevices or network devices, or any other operating system capable ofrunning on the appliance 200 and performing the operations describedherein.

The kernel space 204 is reserved for running the kernel 230, includingany device drivers, kernel extensions or other kernel related software.As known to those skilled in the art, the kernel 230 is the core of theoperating system, and provides access, control, and management ofresources and hardware-related elements of the application 104. Inaccordance with an embodiment of the appliance 200, the kernel space 204also includes a number of network services or processes working inconjunction with a cache manager 232 sometimes also referred to as theintegrated cache, the benefits of which are described in detail furtherherein. Additionally, the embodiment of the kernel 230 will depend onthe embodiment of the operating system installed, configured, orotherwise used by the device 200.

In one embodiment, the device 200 comprises one network stack 267, suchas a TCP/IP based stack, for communicating with the client 102 and/orthe server 106. In one embodiment, the network stack 267 is used tocommunicate with a first network, such as network 108, and a secondnetwork 110. In some embodiments, the device 200 terminates a firsttransport layer connection, such as a TCP connection of a client 102,and establishes a second transport layer connection to a server 106 foruse by the client 102, e.g., the second transport layer connection isterminated at the appliance 200 and the server 106. The first and secondtransport layer connections may be established via a single networkstack 267. In other embodiments, the device 200 may comprise multiplenetwork stacks, for example 267 and 267′, and the first transport layerconnection may be established or terminated at one network stack 267,and the second transport layer connection on the second network stack267′. For example, one network stack may be for receiving andtransmitting network packet on a first network, and another networkstack for receiving and transmitting network packets on a secondnetwork. In one embodiment, the network stack 267 comprises a buffer 243for queuing one or more network packets for transmission by theappliance 200.

As shown in FIG. 2, the kernel space 204 includes the cache manager 232,a high-speed layer 2-7 integrated packet engine 240, an encryptionengine 234, a policy engine 236 and multi-protocol compression logic238. Running these components or processes 232, 240, 234, 236 and 238 inkernel space 204 or kernel mode instead of the user space 202 improvesthe performance of each of these components, alone and in combination.Kernel operation means that these components or processes 232, 240, 234,236 and 238 run in the core address space of the operating system of thedevice 200. For example, running the encryption engine 234 in kernelmode improves encryption performance by moving encryption and decryptionoperations to the kernel, thereby reducing the number of transitionsbetween the memory space or a kernel thread in kernel mode and thememory space or a thread in user mode. For example, data obtained inkernel mode may not need to be passed or copied to a process or threadrunning in user mode, such as from a kernel level data structure to auser level data structure. In another aspect, the number of contextswitches between kernel mode and user mode are also reduced.Additionally, synchronization of and communications between any of thecomponents or processes 232, 240, 235, 236 and 238 can be performed moreefficiently in the kernel space 204.

In some embodiments, any portion of the components 232, 240, 234, 236and 238 may run or operate in the kernel space 204, while other portionsof these components 232, 240, 234, 236 and 238 may run or operate inuser space 202. In one embodiment, the appliance 200 uses a kernel-leveldata structure providing access to any portion of one or more networkpackets, for example, a network packet comprising a request from aclient 102 or a response from a server 106. In some embodiments, thekernel-level data structure may be obtained by the packet engine 240 viaa transport layer driver interface or filter to the network stack 267.The kernel-level data structure may comprise any interface and/or dataaccessible via the kernel space 204 related to the network stack 267,network traffic or packets received or transmitted by the network stack267. In other embodiments, the kernel-level data structure may be usedby any of the components or processes 232, 240, 234, 236 and 238 toperform the desired operation of the component or process. In oneembodiment, a component 232, 240, 234, 236 and 238 is running in kernelmode 204 when using the kernel-level data structure, while in anotherembodiment, the component 232, 240, 234, 236 and 238 is running in usermode when using the kernel-level data structure. In some embodiments,the kernel-level data structure may be copied or passed to a secondkernel-level data structure, or any desired user-level data structure.

The cache manager 232 may comprise software, hardware or any combinationof software and hardware to provide cache access, control and managementof any type and form of content, such as objects or dynamicallygenerated objects served by the originating servers 106. The data,objects or content processed and stored by the cache manager 232 maycomprise data in any format, such as a markup language, or communicatedvia any protocol. In some embodiments, the cache manager 232 duplicatesoriginal data stored elsewhere or data previously computed, generated ortransmitted, in which the original data may require longer access timeto fetch, compute or otherwise obtain relative to reading a cache memoryelement. Once the data is stored in the cache memory element, future usecan be made by accessing the cached copy rather than refetching orrecomputing the original data, thereby reducing the access time. In someembodiments, the cache memory element nat comprise a data object inmemory 264 of device 200. In other embodiments, the cache memory elementmay comprise memory having a faster access time than memory 264. Inanother embodiment, the cache memory element may comprise any type andform of storage element of the device 200, such as a portion of a harddisk. In some embodiments, the processing unit 262 may provide cachememory for use by the cache manager 232. In yet further embodiments, thecache manager 232 may use any portion and combination of memory,storage, or the processing unit for caching data, objects, and othercontent.

Furthermore, the cache manager 232 includes any logic, functions, rules,or operations to perform any embodiments of the techniques of theappliance 200 described herein. For example, the cache manager 232includes logic or functionality to invalidate objects based on theexpiration of an invalidation time period or upon receipt of aninvalidation command from a client 102 or server 106. In someembodiments, the cache manager 232 may operate as a program, service,process or task executing in the kernel space 204, and in otherembodiments, in the user space 202. In one embodiment, a first portionof the cache manager 232 executes in the user space 202 while a secondportion executes in the kernel space 204. In some embodiments, the cachemanager 232 can comprise any type of general purpose processor (GPP), orany other type of integrated circuit, such as a Field Programmable GateArray (FPGA), Programmable Logic Device (PLD), or Application SpecificIntegrated Circuit (ASIC).

The policy engine 236 may include, for example, an intelligentstatistical engine or other programmable application(s). In oneembodiment, the policy engine 236 provides a configuration mechanism toallow a user to identifying, specify, define or configure a cachingpolicy. Policy engine 236, in some embodiments, also has access tomemory to support data structures such as lookup tables or hash tablesto enable user-selected caching policy decisions. In other embodiments,the policy engine 236 may comprise any logic, rules, functions oroperations to determine and provide access, control and management ofobjects, data or content being cached by the appliance 200 in additionto access, control and management of security, network traffic, networkaccess, compression or any other function or operation performed by theappliance 200. Further examples of specific caching policies are furtherdescribed herein.

The encryption engine 234 comprises any logic, business rules, functionsor operations for handling the processing of any security relatedprotocol, such as SSL or TLS, or any function related thereto. Forexample, the encryption engine 234 encrypts and decrypts networkpackets, or any portion thereof, communicated via the appliance 200. Theencryption engine 234 may also setup or establish SSL or TLS connectionson behalf of the client 102 a-102 n, server 106 a-106 n, or appliance200. As such, the encryption engine 234 provides offloading andacceleration of SSL processing. In one embodiment, the encryption engine234 uses a tunneling protocol to provide a virtual private networkbetween a client 102 a-102 n and a server 106 a-106 n. In someembodiments, the encryption engine 234 is in communication with theEncryption processor 260. In other embodiments, the encryption engine234 comprises executable instructions running on the Encryptionprocessor 260.

The multi-protocol compression engine 238 comprises any logic, businessrules, function or operations for compressing one or more protocols of anetwork packet, such as any of the protocols used by the network stack267 of the device 200. In one embodiment, multi-protocol compressionengine 238 compresses bi-directionally between clients 102 a-102 n andservers 106 a-106 n any TCP/IP based protocol, including MessagingApplication Programming Interface (MAPI) (email), File Transfer Protocol(FTP), HyperText Transfer Protocol (HTTP), Common Internet File System(CIFS) protocol (file transfer), Independent Computing Architecture(ICA) protocol, Remote Desktop Protocol (RDP), Wireless ApplicationProtocol (WAP), Mobile IP protocol, and Voice Over IP (VoIP) protocol.In other embodiments, multi-protocol compression engine 238 providescompression of Hypertext Markup Language (HTML) based protocols and insome embodiments, provides compression of any markup languages, such asthe Extensible Markup Language (XML). In one embodiment, themulti-protocol compression engine 238 provides compression of anyhigh-performance protocol, such as any protocol designed for appliance200 to appliance 200 communications. In another embodiment, themulti-protocol compression engine 238 compresses any payload of or anycommunication using a modified transport control protocol, such asTransaction TCP (T/TCP), TCP with selection acknowledgements (TCP-SACK),TCP with large windows (TCP-LW), a congestion prediction protocol suchas the TCP-Vegas protocol, and a TCP spoofing protocol.

As such, the multi-protocol compression engine 238 acceleratesperformance for users accessing applications via desktop clients, e.g.,Microsoft Outlook and non-Web thin clients, such as any client launchedby popular enterprise applications like Oracle, SAP and Siebel, and evenmobile clients, such as the Pocket PC. In some embodiments, themulti-protocol compression engine 238 by executing in the kernel mode204 and integrating with packet processing engine 240 accessing thenetwork stack 267 is able to compress any of the protocols carried bythe TCP/IP protocol, such as any application layer protocol.

High speed layer 2-7 integrated packet engine 240, also generallyreferred to as a packet processing engine or packet engine, isresponsible for managing the kernel-level processing of packets receivedand transmitted by appliance 200 via network ports 266. The high speedlayer 2-7 integrated packet engine 240 may comprise a buffer for queuingone or more network packets during processing, such as for receipt of anetwork packet or transmission of a network packer. Additionally, thehigh speed layer 2-7 integrated packet engine 240 is in communicationwith one or more network stacks 267 to send and receive network packetsvia network ports 266. The high speed layer 2-7 integrated packet engine240 works in conjunction with encryption engine 234, cache manager 232,policy engine 236 and multi-protocol compression logic 238. Inparticular, encryption engine 234 is configured to perform SSLprocessing of packets, policy engine 236 is configured to performfunctions related to traffic management such as request-level contentswitching and request-level cache redirection, and multi-protocolcompression logic 238 is configured to perform functions related tocompression and decompression of data.

The high speed layer 2-7 integrated packet engine 240 includes a packetprocessing timer 242. In one embodiment, the packet processing timer 242provides one or more time intervals to trigger the processing ofincoming, i.e., received, or outgoing, i.e., transmitted, networkpackets. In some embodiments, the high speed layer 2-7 integrated packetengine 240 processes network packets responsive to the timer 242. Thepacket processing timer 242 provides any type and form of signal to thepacket engine 240 to notify, trigger, or communicate a time relatedevent, interval or occurrence. In many embodiments, the packetprocessing timer 242 operates in the order of milliseconds, such as forexample 100 ms, 50 ms or 25 ms. For example, in some embodiments, thepacket processing timer 242 provides time intervals or otherwise causesa network packet to be processed by the high speed layer 2-7 integratedpacket engine 240 at a 10 ms time interval, while in other embodiments,at a 5 ms time interval, and still yet in further embodiments, as shortas a 3, 2, or 1 ms time interval. The high speed layer 2-7 integratedpacket engine 240 may be interfaced, integrated or in communication withthe encryption engine 234, cache manager 232, policy engine 236 andmulti-protocol compression engine 238 during operation. As such, any ofthe logic, functions, or operations of the encryption engine 234, cachemanager 232, policy engine 236 and multi-protocol compression logic 238may be performed responsive to the packet processing timer 242 and/orthe packet engine 240. Therefore, any of the logic, functions, oroperations of the encryption engine 234, cache manager 232, policyengine 236 and multi-protocol compression logic 238 may be performed atthe granularity of time intervals provided via the packet processingtimer 242, for example, at a time interval of less than or equal to 10ms. For example, in one embodiment, the cache manager 232 may performinvalidation of any cached objects responsive to the high speed layer2-7 integrated packet engine 240 and/or the packet processing timer 242.In another embodiment, the expiry or invalidation time of a cachedobject can be set to the same order of granularity as the time intervalof the packet processing timer 242, such as at every 10 ms.

In contrast to kernel space 204, user space 202 is the memory area orportion of the operating system used by user mode applications orprograms otherwise running in user mode. A user mode application may notaccess kernel space 204 directly and uses service calls in order toaccess kernel services. As shown in FIG. 2, user space 202 of appliance200 includes a graphical user interface (GUI) 210, a command lineinterface (CLI) 212, shell services 214, health monitoring program 216,and daemon services 218. GUI 210 and CLI 212 provide a means by which asystem administrator or other user can interact with and control theoperation of appliance 200, such as via the operating system of theappliance 200 and either is user space 202 or kernel space 204. The GUI210 may be any type and form of graphical user interface and may bepresented via text, graphical or otherwise, by any type of program orapplication, such as a browser. The CLI 212 may be any type and form ofcommand line or text-based interface, such as a command line provided bythe operating system. For example, the CLI 212 may comprise a shell,which is a tool to enable users to interact with the operating system.In some embodiments, the CLI 212 may be provided via a bash, csh, tcsh,or ksh type shell. The shell services 214 comprises the programs,services, tasks, processes or executable instructions to supportinteraction with the appliance 200 or operating system by a user via theGUI 210 and/or CLI 212.

Health monitoring program 216 is used to monitor, check, report andensure that network systems are functioning properly and that users arereceiving requested content over a network. Health monitoring program216 comprises one or more programs, services, tasks, processes orexecutable instructions to provide logic, rules, functions or operationsfor monitoring any activity of the appliance 200. In some embodiments,the health monitoring program 216 intercepts and inspects any networktraffic passed via the appliance 200. In other embodiments, the healthmonitoring program 216 interfaces by any suitable means and/ormechanisms with one or more of the following: the encryption engine 234,cache manager 232, policy engine 236, multi-protocol compression logic238, packet engine 240, daemon services 218, and shell services 214. Assuch, the health monitoring program 216 may call any applicationprogramming interface (API) to determine a state, status, or health ofany portion of the appliance 200. For example, the health monitoringprogram 216 may ping or send a status inquiry on a periodic basis tocheck if a program, process, service or task is active and currentlyrunning. In another example, the health monitoring program 216 may checkany status, error or history logs provided by any program, process,service or task to determine any condition, status or error with anyportion of the appliance 200.

Daemon services 218 are programs that run continuously or in thebackground and handle periodic service requests received by appliance200. In some embodiments, a daemon service may forward the requests toother programs or processes, such as another daemon service 218 asappropriate. As known to those skilled in the art, a daemon service 218may run unattended to perform continuous or periodic system widefunctions, such as network control, or to perform any desired task. Insome embodiments, one or more daemon services 218 run in the user space202, while in other embodiments, one or more daemon services 218 run inthe kernel space.

Referring now to FIG. 2B, another embodiment of the appliance 200 isdepicted. In brief overview, the appliance 200 provides one or more ofthe following services, functionality or operations: SSL VPNconnectivity 280, switching/load balancing 284, Domain Name Serviceresolution 286, acceleration 288 and an application firewall 290 forcommunications between one or more clients 102 and one or more servers106. In one embodiment, the appliance 200 comprises any of the networkdevices manufactured by Citrix Systems, Inc. of Ft. Lauderdale Fla.,referred to as Citrix NetScaler devices. Each of the servers 106 mayprovide one or more network related services 270 a-270 n (referred to asservices 270). For example, a server 106 may provide an http service270. The appliance 200 comprises one or more virtual servers or virtualinternet protocol servers, referred to as a vServer, VIP server, or justVIP 275 a-275 n (also referred herein as vServer 275). The vServer 275receives, intercepts or otherwise processes communications between aclient 102 and a server 106 in accordance with the configuration andoperations of the appliance 200.

The vServer 275 may comprise software, hardware or any combination ofsoftware and hardware. The vServer 275 may comprise any type and form ofprogram, service, task, process or executable instructions operating inuser mode 202, kernel mode 204 or any combination thereof in theappliance 200. The vServer 275 includes any logic, functions, rules, oroperations to perform any embodiments of the techniques describedherein, such as SSL VPN 280, switching/load balancing 284, Domain NameService resolution 286, acceleration 288 and an application firewall290. In some embodiments, the vServer 275 establishes a connection to aservice 270 of a server 106. The service 275 may comprise any program,application, process, task or set of executable instructions capable ofconnecting to and communicating to the appliance 200, client 102 orvServer 275. For example, the service 275 may comprise a web server,http server, ftp, email or database server. In some embodiments, theservice 270 is a daemon process or network driver for listening,receiving and/or sending communications for an application, such asemail, database or an enterprise application. In some embodiments, theservice 270 may communicate on a specific IP address, or IP address andport.

In some embodiments, the vServer 275 applies one or more policies of thepolicy engine 236 to network communications between the client 102 andserver 106. In one embodiment, the policies are associated with aVServer 275. In another embodiment, the policies are based on a user, ora group of users. In yet another embodiment, a policy is global andapplies to one or more vServers 275 a-275 n, and any user or group ofusers communicating via the appliance 200. In some embodiments, thepolicies of the policy engine have conditions upon which the policy isapplied based on any content of the communication, such as internetprotocol address, port, protocol type, header or fields in a packet, orthe context of the communication, such as user, group of the user,vServer 275, transport layer connection, and/or identification orattributes of the client 102 or server 106.

In other embodiments, the appliance 200 communicates or interfaces withthe policy engine 236 to determine authentication and/or authorizationof a remote user or a remote client 102 to access the computingenvironment 15, application, and/or data file from a server 106. Inanother embodiment, the appliance 200 communicates or interfaces withthe policy engine 236 to determine authentication and/or authorizationof a remote user or a remote client 102 to have the application deliverysystem 190 deliver one or more of the computing environment 15,application, and/or data file. In yet another embodiment, the appliance200 establishes a VPN or SSL VPN connection based on the policy engine's236 authentication and/or authorization of a remote user or a remoteclient 103 In one embodiment, the appliance 102 controls the flow ofnetwork traffic and communication sessions based on policies of thepolicy engine 236. For example, the appliance 200 may control the accessto a computing environment 15, application or data file based on thepolicy engine 236.

In some embodiments, the vServer 275 establishes a transport layerconnection, such as a TCP or UDP connection with a client 102 via theclient agent 120. In one embodiment, the vServer 275 listens for andreceives communications from the client 102. In other embodiments, thevServer 275 establishes a transport layer connection, such as a TCP orUDP connection with a client server 106. In one embodiment, the vServer275 establishes the transport layer connection to an internet protocoladdress and port of a server 270 running on the server 106. In anotherembodiment, the vServer 275 associates a first transport layerconnection to a client 102 with a second transport layer connection tothe server 106. In some embodiments, a vServer 275 establishes a pool oftranport layer connections to a server 106 and multiplexes clientrequests via the pooled transport layer connections.

In some embodiments, the appliance 200 provides a SSL VPN connection 280between a client 102 and a server 106. For example, a client 102 on afirst network 102 requests to establish a connection to a server 106 ona second network 104′. In some embodiments, the second network 104′ isnot routable from the first network 104. In other embodiments, theclient 102 is on a public network 104 and the server 106 is on a privatenetwork 104′, such as a corporate network. In one embodiment, the clientagent 120 intercepts communications of the client 102 on the firstnetwork 104, encrypts the communications, and transmits thecommunications via a first transport layer connection to the appliance200. The appliance 200 associates the first transport layer connectionon the first network 104 to a second transport layer connection to theserver 106 on the second network 104. The appliance 200 receives theintercepted communication from the client agent 102, decrypts thecommunications, and transmits the communication to the server 106 on thesecond network 104 via the second transport layer connection. The secondtransport layer connection may be a pooled transport layer connection.As such, the appliance 200 provides an end-to-end secure transport layerconnection for the client 102 between the two networks 104, 104′.

In one embodiment, the appliance 200 hosts an intranet internet protocolor intranetIP 282 address of the client 102 on the virtual privatenetwork 104. The client 102 has a local network identifier, such as aninternet protocol (IP) address and/or host name on the first network104. When connected to the second network 104′ via the appliance 200,the appliance 200 establishes, assigns or otherwise provides anIntranetIP, which is network identifier, such as IP address and/or hostname, for the client 102 on the second network 104′. The appliance 200listens for and receives on the second or private network 104′ for anycommunications directed towards the client 102 using the client'sestablished IntranetIP 282. In one embodiment, the appliance 200 acts asor on behalf of the client 102 on the second private network 104. Forexample, in another embodiment, a vServer 275 listens for and respondsto communications to the IntranetIP 282 of the client 102. In someembodiments, if a computing device 100 on the second network 104′transmits a request, the appliance 200 processes the request as if itwere the client 102. For example, the appliance 200 may respond to aping to the client's IntranetIP 282. In another example, the appliancemay establish a connection, such as a TCP or UDP connection, withcomputing device 100 on the second network 104 requesting a connectionwith the client's IntranetIP 282.

In some embodiments, the appliance 200 provides one or more of thefollowing acceleration techniques 288 to communications between theclient 102 and server 106: 1) compression; 2) decompression; 3)Transmission Control Protocol pooling; 4) Transmission Control Protocolmultiplexing; 5) Transmission Control Protocol buffering; and 6)caching. In one embodiment, the appliance 200 relieves servers 106 ofmuch of the processing load caused by repeatedly opening and closingtransport layers connections to clients 102 by opening one or moretransport layer connections with each server 106 and maintaining theseconnections to allow repeated data accesses by clients via the Internet.This technique is referred to herein as “connection pooling”.

In some embodiments, in order to seamlessly splice communications from aclient 102 to a server 106 via a pooled transport layer connection, theappliance 200 translates or multiplexes communications by modifyingsequence number and acknowledgment numbers at the transport layerprotocol level. This is referred to as “connection multiplexing”. Insome embodiments, no application layer protocol interaction is required.For example, in the case of an in-bound packet (that is, a packetreceived from a client 102), the source network address of the packet ischanged to that of an output port of appliance 200, and the destinationnetwork address is changed to that of the intended server. In the caseof an outbound packet (that is, one received from a server 106), thesource network address is changed from that of the server 106 to that ofan output port of appliance 200 and the destination address is changedfrom that of appliance 200 to that of the requesting client 102. Thesequence numbers and acknowledgment numbers of the packet are alsotranslated to sequence numbers and acknowledgement expected by theclient 102 on the appliance's 200 transport layer connection to theclient 102. In some embodiments, the packet checksum of the transportlayer protocol is recalculated to account for these translations.

In another embodiment, the appliance 200 provides switching orload-balancing functionality 284 for communications between the client102 and server 106. In some embodiments, the appliance 200 distributestraffic and directs client requests to a server 106 based on layer 4 orapplication-layer request data. In one embodiment, although the networklayer or layer 2 of the network packet identifies a destination server106, the appliance 200 determines the server 106 to distribute thenetwork packet by application information and data carried as payload ofthe transport layer packet. In one embodiment, the health monitoringprograms 216 of the appliance 200 monitor the health of servers todetermine the server 106 for which to distribute a client's request. Insome embodiments, if the appliance 200 detects a server 106 is notavailable or has a load over a predetermined threshold, the appliance200 can direct or distribute client requests to another server 106.

In some embodiments, the appliance 200 acts as a Domain Name Service(DNS) resolver or otherwise provides resolution of a DNS request fromclients 102. In some embodiments, the appliance intercepts' a DNSrequest transmitted by the client 102. In one embodiment, the appliance200 responds to a client's DNS request with an IP address of or hostedby the appliance 200. In this embodiment, the client 102 transmitsnetwork communication for the domain name to the appliance 200. Inanother embodiment, the appliance 200 responds to a client's DNS requestwith an IP address of or hosted by a second appliance 200′. In someembodiments, the appliance 200 responds to a client's DNS request withan IP address of a server 106 determined by the appliance 200.

In yet another embodiment, the appliance 200 provides applicationfirewall functionality 290 for communications between the client 102 andserver 106. In one embodiment, the policy engine 236 provides rules fordetecting and blocking illegitimate requests. In some embodiments, theapplication firewall 290 protects against denial of service (DoS)attacks. In other embodiments, the appliance inspects the content ofintercepted requests to identify and block application-based attacks. Insome embodiments, the rules/policy engine 236 comprises one or moreapplication firewall or security control policies for providingprotections against various classes and types of web or Internet basedvulnerabilities, such as one or more of the following: 1) bufferoverflow, 2) CGI-BIN parameter manipulation, 3) form/hidden fieldmanipulation, 4) forceful browsing, 5) cookie or session poisoning, 6)broken access control list (ACLs) or weak passwords, 7) cross-sitescripting (XSS), 8) command injection, 9) SQL injection, 10) errortriggering sensitive information leak, 11) insecure use of cryptography,12) server misconfiguration, 13) back doors and debug options, 14)website defacement, 15) platform or operating systems vulnerabilities,and 16) zero-day exploits. In an embodiment, the application firewall290 provides HTML form field protection in the form of inspecting oranalyzing the network communication for one or more of the following: 1)required fields are returned, 2) no added field allowed, 3) read-onlyand hidden field enforcement, 4) drop-down list and radio button fieldconformance, and 5) form-field max-length enforcement. In someembodiments, the application firewall 290 ensures cookies are notmodified. In other embodiments, the application firewall 290 protectsagainst forceful browsing by enforcing legal URLs.

In still yet other embodiments, the application firewall 290 protectsany confidential information contained in the network communication. Theapplication firewall 290 may inspect or analyze any networkcommunication in accordance with the rules or polices of the engine 236to identify any confidential information in any field of the networkpacket. In some embodiments, the application firewall 290 identifies inthe network communication one or more occurrences of a credit cardnumber, password, social security number, name, patient code, contactinformation, and age. The encoded portion of the network communicationmay comprise these occurrences or the confidential information. Based onthese occurrences, in one embodiment, the application firewall 290 maytake a policy action on the network communication, such as preventtransmission of the network communication. In another embodiment, theapplication firewall 290 may rewrite, remove or otherwise mask suchidentified occurrence or confidential information.

C. Client Agent

Referring now to FIG. 3, an embodiment of the client agent 120 isdepicted. The client 102 includes a client agent 120 for establishingand exchanging communications with the appliance 200 and/or server 106via a network 104. In brief overview, the client 102 operates oncomputing device 100 having an operating system with a kernel mode 302and a user mode 303, and a network stack 310 with one or more layers 310a-310 b. The client 102 may have installed and/or execute one or moreapplications. In some embodiments, one or more applications maycommunicate via the network stack 310 to a network 104. One of theapplications, such as a web browser, may also include a first program322. For example, the first program 322 may be used in some embodimentsto install and/or execute the client agent 120, or any portion thereof.The client agent 120 includes an interception mechanism, or interceptor350, for intercepting network communications from the network stack 310from the one or more applications.

The network stack 310 of the client 102 may comprise any type and formof software, or hardware, or any combinations thereof, for providingconnectivity to and communications with a network. In one embodiment,the network stack 310 comprises a software implementation for a networkprotocol suite. The network stack 310 may comprise one or more networklayers, such as any networks layers of the Open Systems Interconnection(OSI) communications model as those skilled in the art recognize andappreciate. As such, the network stack 310 may comprise any type andform of protocols for any of the following layers of the OSI model: 1)physical link layer, 2) data link layer, 3) network layer, 4) transportlayer, 5) session layer, 6) presentation layer, and 7) applicationlayer. In one embodiment, the network stack 310 may comprise a transportcontrol protocol (TCP) over the network layer protocol of the internetprotocol (IP), generally referred to as TCP/IP. In some embodiments, theTCP/IP protocol may be carried over the Ethernet protocol, which maycomprise any of the family of IEEE wide-area-network (WAN) orlocal-area-network (LAN) protocols, such as those protocols covered bythe IEEE 802.3. In some embodiments, the network stack 310 comprises anytype and form of a wireless protocol, such as IEEE 802.11 and/or mobileinternet protocol.

In view of a TCP/IP based network, any TCP/IP based protocol may beused, including Messaging Application Programming Interface (MAPI)(email), File Transfer Protocol (FTP), HyperText Transfer Protocol(HTTP), Common Internet File System (CIFS) protocol (file transfer),Independent Computing Architecture (ICA) protocol, Remote DesktopProtocol (RDP), Wireless Application Protocol (WAP), Mobile IP protocol,and Voice Over IP (VoIP) protocol. In another embodiment, the networkstack 310 comprises any type and form of transport control protocol,such as a modified transport control protocol, for example a TransactionTCP (T/TCP), TCP with selection acknowledgements (TCP-SACK), TCP withlarge windows (TCP-LW), a congestion prediction protocol such as theTCP-Vegas protocol, and a TCP spoofing protocol. In other embodiments,any type and form of user datagram protocol (UDP), such as UDP over IP,may be used by the network stack 310, such as for voice communicationsor real-time data communications.

Furthermore, the network stack 310 may include one or more networkdrivers supporting the one or more layers, such as a TCP driver or anetwork layer driver. The network drivers may be included as part of theoperating system of the computing device 100 or as part of any networkinterface cards or other network access components of the computingdevice 100. In some embodiments, any of the network drivers of thenetwork stack 310 may be customized, modified or adapted to provide acustom or modified portion of the network stack 310 in support of any ofthe techniques described herein. In other embodiments, the accelerationprogram 120 is designed and constructed to operate with or work inconjunction with the network stack 310 installed or otherwise providedby the operating system of the client 102.

The network stack 310 comprises any type and form of interfaces forreceiving, obtaining, providing or otherwise accessing any informationand data related to network communications of the client 102. In oneembodiment, an interface to the network stack 310 comprises anapplication programming interface (API). The interface may also compriseany function call, hooking or filtering mechanism, event or call backmechanism, or any type of interfacing technique. The network stack 310via the interface may receive or provide any type and form of datastructure, such as an object, related to functionality or operation ofthe network stack 310. For example, the data structure may compriseinformation and data related to a network packet or one or more networkpackets. In some embodiments, the data structure comprises a portion ofthe network packet processed at a protocol layer of the network stack310, such as a network packet of the transport layer. In someembodiments, the data structure 325 comprises a kernel-level datastructure, while in other embodiments, the data structure 325 comprisesa user-mode data structure. A kernel-level data structure may comprise adata structure obtained or related to a portion of the network stack 310operating in kernel-mode 302, or a network driver or other softwarerunning in kernel-mode 302, or any data structure obtained or receivedby a service, process, task, thread or other executable instructionsrunning or operating in kernel-mode of the operating system.

Additionally, some portions of the network stack 310 may execute oroperate in kernel-mode 302, for example, the data link or network layer,while other portions execute or operate in user-mode 303, such as anapplication layer of the network stack 310. For example, a first portion310 a of the network stack may provide user-mode access to the networkstack 310 to an application while a second portion 310 a of the networkstack 310 provides access to a network. In some embodiments, a firstportion 310 a of the network stack may comprise one or more upper layersof the network stack 310, such as any of layers 5-7. In otherembodiments, a second portion 310 b of the network stack 310 comprisesone or more lower layers, such as any of layers 1-4. Each of the firstportion 310 a and second portion 310 b of the network stack 310 maycomprise any portion of the network stack 310, at any one or morenetwork layers, in user-mode 203, kernel-mode, 202, or combinationsthereof, or at any portion of a network layer or interface point to anetwork layer or any portion of or interface point to the user-mode 203and kernel-mode 203.

The interceptor 350 may comprise software, hardware, or any combinationof software and hardware. In one embodiment, the interceptor 350intercept a network communication at any point in the network stack 310,and redirects or transmits the network communication to a destinationdesired, managed or controlled by the interceptor 350 or client agent120. For example, the interceptor 350 may intercept a networkcommunication of a network stack 310 of a first network and transmit thenetwork communication to the appliance 200 for transmission on a secondnetwork 104. In some embodiments, the interceptor 350 comprises any typeinterceptor 350 comprises a driver, such as a network driver constructedand designed to interface and work with the network stack 310. In someembodiments, the client agent 120 and/or interceptor 350 operates at oneor more layers of the network stack 310, such as at the transport layer.In one embodiment, the interceptor 350 comprises a filter driver,hooking mechanism, or any form and type of suitable network driverinterface that interfaces to the transport layer of the network stack,such as via the transport driver interface (TDI). In some embodiments,the interceptor 350 interfaces to a first protocol layer, such as thetransport layer and another protocol layer, such as any layer above thetransport protocol layer, for example, an application protocol layer. Inone embodiment, the interceptor 350 may comprise a driver complying withthe Network Driver Interface Specification (NDIS), or a NDIS driver. Inanother embodiment, the interceptor 350 may comprise a min-filter or amini-port driver. In one embodiment, the interceptor 350, or portionthereof, operates in kernel-mode 202. In another embodiment, theinterceptor 350, or portion thereof, operates in user-mode 203. In someembodiments, a portion of the interceptor 350 operates in kernel-mode202 while another portion of the interceptor 350 operates in user-mode203. In other embodiments, the client agent 120 operates in user-mode203 but interfaces via the interceptor 350 to a kernel-mode driver,process, service, task or portion of the operating system, such as toobtain a kernel-level data structure 225. In further embodiments, theinterceptor 350 is a user-mode application or program, such asapplication.

In one embodiment, the interceptor 350 intercepts any transport layerconnection requests. In these embodiments, the interceptor 350 executetransport layer application programming interface (API) calls to set thedestination information, such as destination IP address and/or port to adesired location for the location. In this manner, the interceptor 350intercepts and redirects the transport layer connection to a IP addressand port controlled or managed by the interceptor 350 or client agent120. In one embodiment, the interceptor 350 sets the destinationinformation for the connection to a local IP address and port of theclient 102 on which the client agent 120 is listening. For example, theclient agent 120 may comprise a proxy service listening on a local IPaddress and port for redirected transport layer communications. In someembodiments, the client agent 120 then communicates the redirectedtransport layer communication to the appliance 200.

In some embodiments, the interceptor 350 intercepts a Domain NameService (DNS) request. In one embodiment, the client agent 120 and/orinterceptor 350 resolves the DNS request. In another embodiment, theinterceptor transmits the intercepted DNS request to the appliance 200for DNS resolution. In one embodiment, the appliance 200 resolves theDNS request and communicates the DNS response to the client agent 120.In some embodiments, the appliance 200 resolves the DNS request viaanother appliance 200′ or a DNS server 106.

In yet another embodiment, the client agent 120 may comprise two agents120 and 120′. In one embodiment, a first agent 120 may comprise aninterceptor 350 operating at the network layer of the network stack 310.In some embodiments, the first agent 120 intercepts network layerrequests such as Internet Control Message Protocol (ICMP) requests(e.g., ping and traceroute). In other embodiments, the second agent 120′may operate at the transport layer and intercept transport layercommunications. In some embodiments, the first agent 120 interceptscommunications at one layer of the network stack 210 and interfaces withor communicates the intercepted communication to the second agent 120′.

The client agent 120 and/or interceptor 350 may operate at or interfacewith a protocol layer in a manner transparent to any other protocollayer of the network stack 310. For example, in one embodiment, theinterceptor 350 operates or interfaces with the transport layer of thenetwork stack 310 transparently to any protocol layer below thetransport layer, such as the network layer, and any protocol layer abovethe transport layer, such as the session, presentation or applicationlayer protocols. This allows the other protocol layers of the networkstack 310 to operate as desired and without modification for using theinterceptor 350. As such, the client agent 120 and/or interceptor 350can interface with the transport layer to secure, optimize, accelerate,route or load-balance any communications provided via any protocolcarried by the transport layer, such as any application layer protocolover TCP/IP.

Furthermore, the client agent 120 and/or interceptor may operate at orinterface with the network stack 310 in a manner transparent to anyapplication, a user of the client 102, and any other computing device,such as a server, in communications with the client 102. The clientagent 120 and/or interceptor 350 may be installed and/or executed on theclient 102 in a manner without modification of an application. In someembodiments, the user of the client 102 or a computing device incommunications with the client 102 are not aware of the existence,execution or operation of the client agent 120 and/or interceptor 350.As such, in some embodiments, the client agent 120 and/or interceptor350 is installed, executed, and/or operated transparently to anapplication, user of the client 102, another computing device, such as aserver, or any of the protocol layers above and/or below the protocollayer interfaced to by the interceptor 350.

The client agent 120 includes an acceleration program 302, a streamingclient 306, and/or a collection agent 304. In one embodiment, the clientagent 120 comprises an Independent Computing Architecture (ICA) client,or any portion thereof, developed by Citrix Systems, Inc. of FortLauderdale, Fla., and is also referred to as an ICA client. In someembodiments, the client 120 comprises an application streaming client306 for streaming an application from a server 106 to a client 102. Insome embodiments, the client agent 120 comprises an acceleration program302 for accelerating communications between client 102 and server 106.In another embodiment, the client agent 120 includes a collection agent304 for performing end-point detection/scanning and collecting end-pointinformation for the appliance 200 and/or server 106.

In some embodiments, the acceleration program 302 comprises aclient-side acceleration program for performing one or more accelerationtechniques to accelerate, enhance or otherwise improve a client'scommunications with and/or access to a server 106, such as accessing anapplication provided by a server 106. The logic, functions, and/oroperations of the executable instructions of the acceleration program302 may perform one or more of the following acceleration techniques: 1)multi-protocol compression, 2) transport control protocol pooling, 3)transport control protocol multiplexing, 4) transport control protocolbuffering, and 5) caching via a cache manager. Additionally, theacceleration program 302 may perform encryption and/or decryption of anycommunications received and/or transmitted by the client 102. In someembodiments, the acceleration program 302 performs one or more of theacceleration techniques in an integrated manner or fashion.Additionally, the acceleration program 302 can perform compression onany of the protocols, or multiple-protocols, carried as a payload of anetwork packet of the transport layer protocol.

The streaming client 306 comprises an application, program, process,service, task or executable instructions for receiving and executing astreamed application from a server 106. A server 106 may stream one ormore application data files to the streaming client 306 for playing,executing or otherwise causing to be executed the application on theclient 102. In some embodiments, the server 106 transmits a set ofcompressed or packaged application data files to the streaming client306. In some embodiments, the plurality of application files arecompressed and stored on a file server within an archive file such as aCAB, ZIP, SIT, TAR, JAR or other archive. In one embodiment, the server106 decompresses, unpackages or unarchives the application files andtransmits the files to the client 102. In another embodiment, the client102 decompresses, unpackages or unarchives the application files. Thestreaming client 306 dynamically installs the application, or portionthereof, and executes the application. In one embodiment, the streamingclient 306 may be an executable program. In some embodiments, thestreaming client 306 may be able to launch another executable program.

The collection agent 304 comprises an application, program, process,service, task or executable instructions for identifying, obtainingand/or collecting information about the client 102. In some embodiments,the appliance 200 transmits the collection agent 304 to the client 102or client agent 120. The collection agent 304 may be configuredaccording to one or more policies of the policy engine 236 of theappliance. In other embodiments, the collection agent 304 transmitscollected information on the client 102 to the appliance 200. In oneembodiment, the policy engine 236 of the appliance 200 uses thecollected information to determine and provide access, authenticationand authorization control of the client's connection to a network 104.

In one embodiment, the collection agent 304 comprises an end-pointdetection and scanning mechanism, which identifies and determines one ormore attributes or characteristics of the client. For example, thecollection agent 304 may identify and determine any one or more of thefollowing client-side attributes: 1) the operating system an/or aversion of an operating system, 2) a service pack of the operatingsystem, 3) a running service, 4) a running process, and 5) a file. Thecollection agent 304 may also identify and determine the presence orversions of any one or more of the following on the client: 1) antivirussoftware, 2) personal firewall software, 3) anti-spam software, and 4)internet security software. The policy engine 236 may have one or morepolicies based on any one or more of the attributes or characteristicsof the client or client-side attributes.

In some embodiments and still referring to FIG. 3, a first program 322may be used to install and/or execute the client agent 120, or portionthereof, such as the interceptor 350, automatically, silently,transparently, or otherwise. In one embodiment, the first program 322comprises a plugin component, such an ActiveX control or Java control orscript that is loaded into and executed by an application. For example,the first program comprises an ActiveX control loaded and run by a webbrowser application, such as in the memory space or context of theapplication. In another embodiment, the first program 322 comprises aset of executable instructions loaded into and run by the application,such as a browser. In one embodiment, the first program 322 comprises adesigned and constructed program to install the client agent 120. Insome embodiments, the first program 322 obtains, downloads, or receivesthe client agent 120 via the network from another computing device. Inanother embodiment, the first program 322 is an installer program or aplug and play manager for installing programs, such as network drivers,on the operating system of the client 102.

D. Multi-Mode Transport Layer Compression Technique

Referring now to FIG. 4, an embodiment of the appliance 200 is depictedfor providing a technique of transmitting compressed and decompressedcontent via the same transport layer connection between a client 102 andserver 106. In some embodiments, the appliance 200 identifies andselects a type of compression from a plurality of compression techniques410 to perform on a per communication basis, such as on a serverresponse to a client's request. In other embodiments, the appliance 200dynamically switches between applying and not applying compression tothe flow of network traffic to a client 102 from a server 106 a-106 nvia the same transport layer connection. In brief overview of FIG. 4,the appliance 200 includes a compression engine 238 having multi-modecompression functionality 400. The compression engine 238 may use one ormore compression techniques 420 on a server response having one or moreobjects 425. The policy engine 236 may have one or more compressionpolicies 410 associated with object or data types. The compressionengine 238 may perform and apply a type of compression from theplurality of compression techniques 420 in accordance with a compressionpolicy 410.

The multi-mode compression portion 400 of the compression engine 238 maycomprise software, hardware, or any combination of software andhardware. The multi-mode compression engine 400 comprises logic,function, operations or any type and form of executable instructions todetermine whether to apply a compression technique to a communication,to identify the compression technique to apply to the communication, andto perform the identified compression on the communication. In someembodiments, the appliance 200 via the multi-mode compression engine 400compresses some of the communication via the client's transport layerconnection to a server 206 and leaves some of the communicationdecompressed. In one embodiment, the multi-mode compression engine 400compresses application layer data carried by a transport layer protocol.In another embodiment, the multi-mode compression engine 400 compressesa portion of a payload carried via the transport layer. For example, themulti-mode compression engine 400 may compress objects or other portionsof data, such as one or more objects transmitted via HTTP.

The plurality of compression types 420 include a wide range of differenttypes and forms of compression techniques. In some embodiments, thecompression type 420 include and type and form of lossless compressiontechniques. In one embodiment, a compression type 420 includes anyversion of GNU zip or gzip. In some embodiments, a compression type 420includes compression provided by the zlib library, distributed viawww.zlib.net. In another embodiment, a compression type 420 includes adeflate compression technique. In other embodiments, the compressiontype 420 includes a delta or differential compression technique. In someembodiments, a compression type includes and type and form of aLempel-Zip algorithm, such as the LZ777 and LZ88 lossless datacompression algorithms. In one embodiment, the compression types 420includes run-length encoding compression. In other embodiments, thecompression type 420 includes a Burrows-Wheeler transform (BWT), alsoreferred to as block-sorting compression. In another embodiment, thecompression type 420 includes a prediction by partial matching (PPM) oran adaptive statistical data compression technique.

In some embodiments, the compression type 420 includes a context mixingtechnique, is a type of data compression algorithm in which thenext-symbol predictions of two or more statistical models are combinedto yield a prediction that is often more accurate than any of theindividual predictions. In one embodiment, the compression type 420include PAQ, an open source data compression archiver. In otherembodiments, the compression type 420 includes an entropy encodingscheme that assigns codes to symbols so as to match code lengths withthe probabilities of the symbols. In one embodiment, the compressiontype 420 includes a Huffman coding or an adaptive Huffman codingtechnique, such as the Vitter algorithm or the Faller-Gallager-Knuth(FGN) technique. In some embodiments, the compression type 420 includesbzip2, a combination of the Burrows-Wheeler transform and Huffmanencoding. In some embodiments, for audio and/or video data, thecompression type includes any type and form of lossy compressionalgorithms.

The client 102 and/or server 106 may transmit a request or response,respectively, comprise one or more objects 425. In some embodiments, theobject 425 is the content or type of content included in thecommunication, such as a server's response to a client 102. The contentor type of object 425 may be binary or ASCII. In other embodiments, theobject 425 comprises data known to be from a type of application or havean associated type of data for the application. For example, the object425 may comprise application related content such as MacromediaFlashplayer or Microsoft Presentation. In one embodiment, the object 425comprises any data that is transmitted via Hypertext Markup Language(HTML), or Extensible Markup Language (XML). In yet another embodiment,the object 425 comprises a file, or content thereof. In someembodiments, the object 425 comprises data retrieved from a database.

Still referring to FIG. 4, the appliance 200 may include one or morecompression policies 410. In some embodiments, the policy engine 236provides the compression policies 410. In other embodiments, thecompression engine 238 provides the compression policies 410. In oneembodiment, the compression policy 410 identifies a type of compression420 to apply to a communication based on the type of object 425 includedin the communication. For example, a compression policy 420 may identifythe type of compression to perform on the object if the object is ASCII.In another example, the compression policy 420 may identify the type ofcompression on the object if the object is binary and associated with aknown or predetermined application. In another embodiment, thecompression policy 410 identifies a type of compression 420 to applybased on the type of protocol identified in the response and/or request.In some embodiments, the compression policy 410 identifies a type ofcompression 420 to apply based on the type or location of the service270 a-270 n, and/or server 106 a-106 n. In yet other embodiments, thecompression policy 410 identifies a type of compression 420 to usedbased on any of the IP or network layer information of thecommunication, such as destination IP address, source IP address,destination port or source port. In some embodiments, the compressionpolicy 420 indicates not to compress the communication.

In operation and as illustrated by way of example in FIG. 4, theappliance 200 may apply different compression types 420 to responses tothe same client 102 b and/or among different clients 102 a-102 n. Forexample, a server 106 a may serve a first response and second responseto a client 102 a via the appliance 200. The first and second responsemay comprise decompressed data. Via the multi-mode compression engine400 and compression policies 420, the appliance 200 may transmit thefirst response decompressed to the client 102 a and the second responsecompressed using a first compression type 420 to the client 102 a. Aserver 106 b may serve a first and second response to client 102 b viathe appliance 200. In this case, the application 200 may compress bothresponses to the client 102 b using a first compression type 420 for thefirst response and a second compression types 420 for the secondresponse. In yet another example, the appliance 200 may apply a thirdcompression type 420 to one of the responses from server 106 n to client102 n. The appliance 200 may determine the compression type or not tocompress based on the object 425 content or type in the response orrequest. On a per request and/on per response basis, the appliance 200may apply one of a plurality of compression types 420 to thecommunication, which may include not compressing the communication. Inone embodiment, the appliance 200 transmits both compressed anddecompressed responses via the same transport layer connection to theclient 102.

Referring now to FIG. 5, steps of an embodiment of a method 500 forpracticing multi-mode compression techniques is depicted. In briefoverview, at step 505, the client agent 120 establishes a connectionwith the appliance 200, such as a transport layer connection. At step510, the appliance 200 receives a response from the server 106 to arequest of the client 102. The response may comprise decompressed dataor data already compressed. At step 515, the appliance 200 determineswhether to compress the received response. If the appliance 200 decidesto not compress the response, the appliance 200, at step 520, transmitsthe response to the client 102 without performing a compression. If theappliance 200 decides to compress the response, the appliance, at step525, identifies one compression type from a plurality of compressiontypes 420. For example, the appliance 200 selects a compression type 420based on a compression policy 410. At step 530, the appliance 200compresses the response based on the identified compression type, and atstep 535, transmits the compressed response to the client agent 120. Atstep 540, the client agent 120 decompresses the compressed response andprovides the decompressed content to an application, such as a webbrowser.

In further detail, at step 505, the client agent 120 establishes atransport layer connection with the appliance 200, such as via thetransport control protocol or user datagram protocol. In one embodiment,the client agent 120 establishes a tunnel connection with the appliance200 using any type and form of tunneling protocol. In anotherembodiment, the client agent 120 establishes a virtual private networkconnection via the appliance 200 to a network 104. For example, theclient agent 120 may establish a virtual private network connection withthe appliance 200 to connect the client 102 on the first network 104 toa second network 104′. In some embodiments, the client agent 120establishes a SSL VPN connection with the appliance 200. In yet anotherembodiment, the client agent 120 establishes a tunnel or virtual privatenetwork connection using Transport Layer Secure (TLS) protocol. In oneembodiment, the client agent 120 establishes a tunnel connection usingthe Common Gateway Protocol (CGP) manufactured by Citrix Systems, Inc.of Ft. Lauderdale, Fla.

At step 510, the appliance 200 receives a response from the server 106to a request of the client 102. In one embodiment, the appliance 200intercepts the response from the server 106 during transmission to theclient 102. In other embodiments, the server 106 transmits the responseto the appliance 200 to forward to the client 102. In some embodiments,the server 106 transmits the response in response to a request from aclient 102. In other embodiments, the server 106 transmits the responseasynchronously to the client 102. In another embodiment, the responsefrom the server 106 comprises a request to the client 102, such as arequest for information, such as an object, e.g., a client certificate.In one embodiment, the response from the server 106 comprisesdecompressed data. In another embodiment, the response from the server106 comprises compressed data. In some embodiments, the response fromthe server 106 comprises compressed and decompressed data.

At step 515, the appliance 200 and/or multi-mode compression engine 400determines whether to compress the response received or intercepted fromthe server 106. The appliance 200 may determine to compress or not tocompress based on any information related to the response, such ascontent, protocol, source and destination information. In oneembodiment, the appliance 200, such as via the multi-mode compressionengine 400, inspects or analyzes the content of the response for one ormore objects 425. In some embodiments, the appliance 200 determines thetype or content of the object 425. In other embodiments, the appliance200 determines if the response is already compressed or has anycompressed portions. For example, in one embodiment, the appliance 200determines if an object of the response is already compressed. Inanother embodiment, the appliance 200 determines the type of protocolused in the response. In some embodiments, the appliance 200 determinesfrom any network or IP layer information, such as destination and/orsource IP address, or destination and/or source port, whether tocompress the response.

If the appliance 200 decides not to compress the response, the appliance200, at step 520, transmits the response to the client 102 withoutperforming a compression. In one embodiment, the appliance 200determines the response is already compressed. In another embodiment,the appliance 200 determines the response is decompressed and based onthe type of object 425, a compression policy 410 indicates the responseshould not be compressed by the appliance 200. For example, thecompression policy 410 may indicate if the response is shorter than apredetermined length then the response should not be compressed. Inanother example, the compression policy 410 may indicate if the responsecomprises binary data from an application that the response should notbe compressed. In another embodiment, the appliance 200 determines notto compress the response based on tracking compression statistics onresponses based on the content or type of object 425, or based oncompressibility statistics of responses from the server 106 or service270. For example, if the compressibility of responses from the server106 do not meet a predetermined compressibility threshold over time, theappliance 200 may not continue compressing responses from that server106.

At step 535, in some embodiments, the appliance 200 decides to compressthe response. In one embodiment, the appliance 200 and/or multi-modecompression engine 200 determines the content or type of object 435 ofthe response can be compressed into a size meeting a predeterminedcompressibility threshold. In some embodiments, the appliance 200decides to compress the response based on a compression policy 410indicating that the content or type of object 420 should be compressedby the appliance 200. In another embodiment, a compression policy 410indicates to compress responses from the server 106 or service 270. Inone embodiment, the appliance 200 decides to compress the response basedon a compression policy 410 indicating that the response should becompressed based on the protocol or type of protocol used by theresponse.

Further to step 525, in one embodiment, the appliance 200, such as viathe multi-mode compression engine 400, identifies one compression typefrom a plurality of compression types 420 for compressing the response.For example, the appliance 200 selects a compression type 420 based on acompression policy 410. In some embodiments, the appliance 200 selects acompression type 420 based on the content or type of object 425, theprotocol or type of protocol used by the response, or the network or IPlayer identified by the response. In another embodiment, the client 102and/or client agent 120 identifies to the appliance 200 the compressiontype 420 to use for responses transmitted to the client 102. In yetanother embodiment, the appliance 200 selects the compression type 420based on the selection type used for a previous response. In someembodiments, the appliance 200 selects the compression type 420 based onattributes of the client 102 and/or server 106. In one embodiment, theappliance 200 selects the compression type 420 based on the type ofprotocol used in the response, or between the client 102 and server 106.In some embodiments, the appliance 200 selects a first compression type420 for a first object 425 of the response, and a second compressiontype 420 for a second object 425 of the response.

At step 530, the appliance 200, such as via multi-mode compressionengine 400, compresses the response based on the identified or selectedcompression type 420. In one embodiment, the appliance 200 compressesthe entire payload of the transport layer packet using the selectedcompression type 420. In another embodiment, the appliance 200compresses a portion of the payload of the response using the selectedcompression type 420. In some embodiments, the appliance 200 compressesan object 425 of the response using the selected compression type 420.In yet another embodiment, the appliance 200 compresses a first object425 and a second object 425 of the response with the selectedcompression type 420. In some embodiments, the appliance 200 compressesa first object 425 of the response with a first selected compressiontype 420 and a second object of the response with a second selectedcompression type 420.

At step 535, the appliance 200 transmits the compressed response to theclient agent 120 or client 102. In one embodiment, the appliance 200transmits a plurality of responses in a compressed form to the clientagent 120. In other embodiments, the appliance 200 transmits eachresponse separately in a compressed form to the client agent 120. Insome embodiments, the appliance 200 transmits the type of compression420 to the client agent 120. In one embodiment, the appliance 200identifies the compression type 420 via the payload of the compressedresponse. In another embodiment, the appliance 200 identifies thecompression type 420 via a communication over the transport layerconnection to the client agent 120 or via an out-of-band or othercommunication channel to the client agent 120.

At step 540, the client agent 120 decompresses the compressed responseand provides the decompressed content to an application, such as a webbrowser. In one embodiment, the client agent 120 decompresses thecompressed response upon receipt. In other embodiments, the client agent120 decompresses the compressed response upon receiving a predeterminednumber of responses, or a predetermined quantity of data via theresponse. In one embodiment, the client agent 120 decompresses theentire response. In some embodiments, the client agent 120 decompressesa portion of the response. In another embodiment, the client agent 120decompresses each compressed object 425 of the response. In someembodiments, the client agent 120 provides the decompressed content ofthe response via the network stack 310 of the client 102. In otherembodiments, the client agent 120 communicates the decompressedresponse, or content thereof, via an application programming interfaceor function call. In yet another embodiment, the client agent 120provides the compressed response to the application of the client 102and the application decompresses the content.

In some embodiments, the client agent 120, transparently to anapplication or user of the client 102, receives the compressed response,decompresses the compressed response and provides the decompressedresponse to the application. For example, in one embodiment, theapplication, such as a web browser, may not support the compression type420 used by the appliance 200 to compress the response. With the clientagent 120, the application may receive the decompressed content althoughthe application may have not otherwise recognized the compressedcontent. As such, in some embodiment, the client agent 120 and appliance200 perform compression on responses to accelerate delivery of theresponse in a manner transparent or non-intrusive to the application.

Although an embodiment of method 500 is generally described above inview of responses from a server 106 to a client 102, the method 500, insome embodiments, may be used to compress requests from the client 102to the server 106. For example, a client 102 may transmit to the server106 a request comprising one or more objects 425. The multi-modecompression engine 400 may determine to compress the request or theseobjects, and select a compression type 420 based on a compression policy410 or information identified via the request, such as protocol, type orcontent of object 425, or any network or IP related information. Theappliance 200 may compress the request using the determined or selectedcompression type and then transmit the compresses request to a server106. Furthermore, method 500 may be practiced bi-directionally for bothrequests and responses to provide compression to and from a client 102,or to and from a server 106. As such, in one embodiment, the multi-modecompression technique of the appliance 200 may be used to transmit bothcompressed and uncompressed content via the same transport layerconnection in a manner transparent to an application on the client 102and/or service 270 on the server 106.

Additionally, the method 500 may be practiced so that the appliance 200may apply different compression types 420 to each client 102 and/orserver 106. For example, the appliance 200 may compress content for afirst client 102 a using a first and/or second compression type 420, andfor a second client 102 b using a second and/or third compression type.In another example, the appliance may compress responses from a firstserver 106 using a first compression type 420 and may compressesresponses from a second server 106 b using a second or third compressiontype 420. The method 500 may also be practiced so that the appliance 200used different compression techniques for the same clients and/orservers at different times. For example, the appliance 200 may compressa first response from a first server 106 a using a first compressiontype 420, and then may compress a subsequent response from the firstserver 106 a using a second compression type 420. In some embodiments,the compression policy 410 may be changed dynamically or on the fly toapply a different compression type 420 to a network communicationcompressed by the appliance 200.

In view of the structure, function, and operations of the appliance 200and client agent 120 described herein, the multi-mode compression engine400 and technique 500 provides for the transmission of compressed anduncompressed content over the same transport layer connection between aclient 102 and a server 106. The appliance 200 and/or client agent 120can accelerate or otherwise improve the speed of delivery of content orthe transmission of network communications between a client and serverin a manner not dependent on the compression capabilities or compressionawareness of the application on the client 102 and/or the application270 on the server 106. Additionally, the appliance 200 can apply one ofa plurality of compression techniques to network communications based ona compression policy and/or information associated with thecommunication, such as IP layer information, protocol, or content ortype of object of the communications. In this manner, the appliance 200can apply a better, more desired or more suitable compression techniqueto the communication, which in turn may help further accelerate thedelivery of the communication.

1. A method for communicating compressed and uncompressed content over atransport layer connection established by an appliance between a clientand a server, the method comprising the steps of: (a) establishing, byan appliance, a transport layer connection between a client and aserver; (b) receiving, by the appliance, a first response from theserver to a first client request, and a second response from a serviceexecuting on the server to a second client request, the first responseand the second response comprising a plurality of uncompressed dataobjects; (c) transmitting, by the appliance, the first response to theclient; (d) identifying, by the appliance and responsive to acompression policy, a first type of compression from a plurality ofcompression types for compressing a first object of the plurality ofuncompressed data objects in the second response to the client and asecond type of compression from the plurality of compression types forcompressing a second object of the plurality of uncompressed dataobjects in the second response to the client, the compression policyidentifying the first type of compression based on the content or typeof the first object, and identifying the second type of compressionbased on a protocol of the second object of the plurality ofuncompressed data objects; (e) compressing, by the appliance, the firstobject in the second response based on the identified first compressiontype and the second object in the second response based on theidentified second compression type; and (f) transmitting, by theappliance, the compressed second response to the client.
 2. The methodof claim 1, comprising determining, by the appliance, a type of objectincluded in one of the first response or the second response.
 3. Themethod of claim 2, comprising identifying, by the appliance, the type ofcompression for compressing the second response based on the type ofobject.
 4. The method of claim 3, comprising configuring, via theappliance, a rule identifying the type of compression associated withthe type of object.
 5. The method of claim 1, wherein identifying afirst type of compression further comprises identifying, by theappliance, the first type of compression from the plurality ofcompression types for compressing the second response based on an objectin the response, as indicated by the compression policy.
 6. The methodof claim 1, wherein the type of compression comprises one of thefollowing: a gzip compression, a deflate compression, and a deltacompression.
 7. The method of claim 1, comprising identifying, by theappliance, for a third response to the client a second type ofcompression from the plurality of compression types, compressing thethird response based on the second type of compression, and transmittingthe compressed third response to the client.
 8. The method of claim 1,comprising identifying, by the appliance, for a third response to asecond client a second type of compression from the plurality ofcompression types, compressing the third response based on the secondtype of compression, and transmitting the compressed third response tothe second client.
 9. The method of claim 1, comprising establishing, bythe appliance, a Secure Socket Layer (SSL) session via the transportlayer connection between the client and the server.
 10. The method ofclaim 1, comprising accelerating, by the appliance, transmission of oneof the first response or the compressed second response using one ormore of the following techniques: Transport Control Protocol (TCP)connection pooling; TCP connection multiplexing; TCP buffering; andcaching.
 11. A system for communicating compressed and uncompressedcontent over a transport layer connection established by an appliancebetween a client and a server, the system comprising: means forestablishing, by an appliance, a transport layer connection between aclient and a server; means for receiving, by the appliance, a firstresponse from the server to a first client request, and a secondresponse from a service executing on the server to a second clientrequest, the first response and the second response comprising aplurality of uncompressed data objects; means for transmitting, by theappliance, the first response to the client; means for identifying, bythe appliance and responsive to a compression policy, a first type ofcompression from a plurality of compression types for compressing afirst object of the plurality of uncompressed data objects in the secondresponse to the client and a second type of compression from theplurality of compression types for compressing a second object of theplurality of uncompressed data objects in the second response to theclient, the compression policy identifying the first type of compressionbased on the content or type of the first object, and identifying thesecond type of compression based on a protocol of the second object ofthe plurality of uncompressed data objects; means for compressing, bythe appliance, the first object in the second response based on theidentified first compression type and the second object in the secondresponse based on the identified second compression type; and means fortransmitting, by the appliance, the compressed second response to theclient.
 12. The system of claim 11, comprising means for determining, bythe appliance, a type of object included in one of the first response orthe second response.
 13. The system of claim 12, comprising means foridentifying, by the appliance, the type of compression for compressingthe second response based on the type of object.
 14. The system of claim13, comprising means for configuring, via the appliance, a ruleidentifying the type of compression associated with the type of object.15. The system of claim 11, wherein means for identifying a first typeof compression further comprises means for identifying, by theappliance, the first type of compression from the plurality ofcompression types for compressing the second response based on an objectin the response, as indicated by the compression policy.
 16. The systemof claim 11, wherein the type of compression comprises one of thefollowing: a gzip compression, a deflate compression, and a deltacompression.
 17. The system of claim 11, comprising means foridentifying, by the appliance, for a third response to the client asecond type of compression from the plurality of compression types,compressing the third response based on the second type of compression,and transmitting the compressed third response to the client.
 18. Thesystem of claim 11, comprising means for identifying, by the appliance,for a third response to a second client a second type of compressionfrom the plurality of compression types, compressing the third responsebased on the second type of compression, and transmitting the compressedthird response to the second client.
 19. The system of claim 11,comprising means for establishing, by the appliance, a Secure SocketLayer (SSL) session via the transport layer connection between theclient and the server.
 20. The system of claim 11, comprising means foraccelerating, by the appliance, transmission of one of the firstresponse or the compressed second response using one or more of thefollowing techniques: Transport Control Protocol (TCP) connectionpooling; TCP connection multiplexing; TCP buffering; and caching.
 21. Amethod for communicating compressed and uncompressed content over atransport layer connection established by an appliance between a clientand a server, the method comprising the steps of: (a) establishing, byan appliance, a transport layer connection between a client and aserver; (b) receiving, by the appliance, a first response from theserver to a first client request, and a second response from a serviceexecuting on the server to a second client request, the first responseand the second response comprising a plurality of uncompressed dataobjects; (c) transmitting, by the appliance, the first response to theclient; (d) identifying, by the appliance and responsive to acompression policy, a first type of compression from a plurality ofcompression types for compressing a first object of the plurality ofuncompressed data objects in the second response to the client and asecond type of compression from the plurality of compression types forcompressing a second object of the plurality of uncompressed dataobjects in the second response to the client, the compression policyidentifying the first type of compression based on the content or typeof the first object, and identifying the second type of compressionbased on a protocol of the second object; (e) compressing, by theappliance, the first object in the second response based on theidentified first compression type and the second object in the secondresponse based on the identified second compression type; and (f)transmitting, by the appliance, the compressed second response to aclient agent, executing on the client, configured to intercept anddecompress the compressed second response and provide the decompressedsecond response to an application executing on the client, theapplication unaware of the compression.